Aromatic hydrogenation using a fluorided alumina catalyst



United States Patent OfiFlce 3,435,085 Patented Mar. 25, 1969 3 435 085Anon/mare rrYniaodnNATroN USING A FLUOREDED ALUMINA CATALYST Robert J.White, Piuole, and Robert J. Houston, San

hydrocarbons in the presence of sulfur, catalysts containing largeamounts of fluorine are outstanding in thelr properties and are not theequivalent of the large group of superficially similarcatalystsdisclosed in the prior art. Specifically, it has now beendiscovered that, by employ- Rafael, Zlssigmrs. g Chevron .Resem'ch 5 ingthe catalysts hereinafter described in a hydrogenation P San P51319159;Calif" a corporation of Delaware process in which sulfur is presentunexpectedly high de- No Drawing. Fried Sept. 25, 1967, Ser. No. 676,3840 b d It h Em CL C07: 5/10, 5/14 .,rees of hydrogenation conversion canbe 0 tame as Us, (:1, 26() 667 7 Chi also been discovered that thesehydrogenation :cat alysts 10 retain an unexpectedly high degree of theiractivity 1n the presence of sulfur. f h d I JRE The process of thisinvention is a process or y ro- ABSTRACT OF DISCLOS genating aromatichydrocarbons, which comprises con- Aromatics are hydrogenated m thePrgsence of sulfur tacting said hydrocarbons with hydrogen in thepresence over a catalyst cohtalmng Group vnhhydrogenanon of sulfur andan essentially nonsiliceous catalyst commetal disposed on an essentiallynonsrlrceous support prising a Group VIII hydrogenation metal disposedon 3 comprising alumina and 10-35 percent fluorine. Platinum SupportComprising alumina and at least 10 percent is the preferred Group VIIImetal. The catalyst retains fiuOn-na a high degree of activity in thepresence of up to 3 per- In a more preferred embodiment, the Group VIIIn Sulfur ill the feedmetal is a noble metal; and, in a still morepreferred embodiment, the noble metal is platinum. BACKGROUND OF THEINVENTION DETAILED DESCRIPTION OF THE INVENTION T is n en relates toProcesses the CEltalytic The process of this invention involveshydrogenating hydtogohatioh of aromatic hydrocarbons; ill P aromaticcompounds by contacting them with hydrogen tioulaf, it relates toProcesses the hydrogenation of in the presence of sulfur and a highfluorine content, esalomatl'o hydrocarbons in the PresehCe of Sulfur yuse sentially nonsiliceous Group VIII metal-containing cat ofIloIlSihooouS catalyst Containing greater than 10 P alyst. This catalysthas been found to be both unexpectedcent fluorine. ly sulfur resistantand also highly active. Its activity is General Processes for thehydrogenation f aromatic considerably higher than that of other knownfluorided ydrocarbons are well known and are utilized for many aluminacatalysts. Such other catalysts generally have purposes. Numerouscatalysts have been used to promot very low fluorine contents and, infact, the prior art genhydrogcnation. Among the catalysts described inthe prior erally teaches that it is undesirable to raise fluorine conartare what are often referred to as fluoride catalysts. tents of thesecatalysts above a few weight percent and In general, these catalysts arecomposed of any one of that 10 weight percent fluorine is an absolutemaximum. several types of supports, most of which contain silica,Typical of these other catalysts are the naphtha rea hydrogenation metalsuch as a Group VI or Group VIII forming catalysts. metal, and a smallamount of fluorine, usually referred It has now been discovered,however, that for substanto as a promoter. The fluorine promoter ispresent to tial aromatic hydrogenation in the presence of sulfur highthe extent of up to a few percent by Weight of the cat- 46 fluoridelevel, which is defined to be above 10 weight alyst. In many cases, thefluorine promoter is disclosed percent fluorine measured as the element,is not only to be optional and used only where the support itself isdesirable but, in fact, is necessary. Table I illustrate the notsufliciently acidic. surprising order of magnitude increase inhydrogenation It is commonly reported in the prior art that hydroactivity obtained by use of high fluorine content catalysts genationcatalysts are extremely susceptible to sulfur of the type describedherein when compared to similar poisoning. Consequently, substantialeffort and expense catalysts containing low fluorine contents. Theexmust be incurred to remove sulfur from the aromatic hyerimentsillustrated in Table I were made by passing drocarbon feed which is tobe hydrogenated. Much effort, benzene, containing sulfur as dimethyldisulfide, over the fruitless until now, has been expended to develop acatalumina-supported catalysts in the presence of hydrogen alyst whichwould retain its hydrogenation activity in 50 at 725 F., 1,200 p.s.i.a.,HSV of 3, and a hydrogen-tothe presence of sulfur. hydrocarbon ratio inthe feed of 10.

TABLE I Catalysts A B C D E Hydrogenation metal Pl; Pt Pt Ni Ni Metalcontent, wt. percent 0. 37 0.37 O. 37 15 15 Fluorine content, wt.percent O. 50 17 17 0 14. 5 Hydrogenation activity (HA), defined K asmole percent of benzene converted HA SC, wt. HA SC, Wt. HA SC, wt. HASC, HA S0, at 725 F. at various sulfur contents percent S percent Spercent S p.p.m. S p p.m. S (SC) measured as p.p.1n. of sulfur 0r wt.percent sulfur Hours on stream:

SUMMARY OF THE INVENTION The present invention is based upon thediscovery that, for

the purpose of substantially hydrogenating aromatic 5 a large amount ofsulfur is present in the feed.

It is apparent from the data of Table I that the high fluorine contentcatalysts increase hydrogenation of aromatic compounds by an order ofmagnitude even though This resalt is completely unanticipated andunexpected from the teaching of the prior art.

The catalyst employed in this invention comprises a Group VIIIhydrogenation metal disposed on a support comprising alumina and greaterthan weight percent fluorine. The Group VIII hydrogenation metal may beany of the three iron group or six noble metals. As illustrated in TableI, the noble metals are preferred; and particularly preferred among thenoble metals is platinum. The hydrogenation metal may be present in anamount up to Weight percent of the catalyst. When using the noblemetals, it is preferred to have a low metal content, such as 0.1-3weight percent. The support for the catalyst must be essentiallynonsiliceous, for at the high fluorine contents used in this catalystsubstantial fluorine-silica reactions often occur, causing formation ofvolatile fluosilicate compounds and subsequent collapse of the catalystand plugging of the catalyst bed. Preferably no silica at all should bepresent. However, a very small amount, no more than about 1 or 2 weightpercent of the catalyst, can be tolerated in some instances when thetotal fluorine content is to be at or only slightly above 10 weightpercent.

The fluorine content must be above 10 weight percent, and is preferablyin the range of 1235 weight percent. Fluorine may be added to thecatalyst either before or after the metal is added. The fluorine may beincorporated into the catalyst by contacting the alumina support with agaseous or liquid fluorine compound. A particularly preferred method offluoriding the catalyst is to pass a gaseous mixture of hydrogen andhydrogen fluoride over an alumina support to which the desired amount ofmetal has previously been added. This generally causes a stoichiometricconversion of alumina to aluminum fluoride and may be continued untilthe desired amount of fluorine has been incorporated into the catalyst.Another satisfactory method of incorporating fluorine into the catalystis to contact the alumina support, to which metal has previously beenadded, with a solution of ammonium fluoride. Catalysts fluorided by thelatter procedure do not appear to be as active as those fluorided withthe I-IF/hydrogen mixture. They are, however, considerably andunexpectedly more active than the low fluorine content catalystsdisclosed in the prior art.

Aromatic hydrogenation in the presence of sulfur with the catalystherein described is conducted at a temperature in the range of 650900F., a pressure above 500 p.s.i.a., preferably in the range of 1,000-4,000 p.s.i.a., a liquid hourly space velocity (LI-ISV) of 0.2-10, and aratio of hydrogen-to-hydrocarbon in the feed of 1:1-20z1.

In some instances, it may be desirable to increase the the activity of ahigh fluorine content catalyst by heating the catalyst in a reducingatmosphere prior to its use for hydrogenation. This heat activation iscommonly conducted in the temperature range of 8001,300 F. Suchactivation should be used judiciously, however; for in some cases hightemperature activation, although creating an initial high activity ofthe catalyst, causes the catalyst to deactivate relatively rapidly. Thisdeactivation appears to be more pronounced when the heat activation hasbeen conducted above 1,000 F.

The process of this invention, as contrasted to conventionalhydrogenation processes with nonfluorided or low fluorine contentcatalysts, provides a method for obtaining significant hydrogenation ofsulfur-containing, unsaturated feedstocks. Sulfur contents of up toabout 3 percent based on feed can be tolerated by the high fluorinecontent catalysts of this process. This will significantly reduce theamount of desulfurization that must be performed on hydrogenation fuelsand, in many cases, will eliminate entirely the need for separate andexpensive desulfurization steps prior to hydrogenation.

It is apparent that many widely different embodiments of this inventionmay be made without departing from the scope and spirit thereof; and,therefore, it is not intended to be limited except as indicated in theappended claims.

We claim:

1. A process for the hydrogenation of aromatic hydrocarbons in thepresence of sulfur which comprises contacting said aromatic hydrocarbonswith hydrogen in the presence of sulfur and an essentially silica-freecatalyst comprising a Group VIII metal on a refractory supportcomprising alumina and at least 10 weight percent fluorine.

2. The process of claim 1 wherein the Group VIII hydrogenation metal isa noble metal.

3. The process of claim 2 wherein the noble metal is platinum.

4. The process of claim 1 wherein the fluorine content of the catalystis in the range of 12-35 weight percent.

5. The process of claim I wherein the catalyst is activated afterformation by heating in a reducing atmosphere at a temperature at leastas high as the temperature at which the hydrogenation is to beperformed.

6. The process of claim 5 wherein the catalyst is activated at atemperature in the range of 700- 0 F.

7. The process of claim 1 wherein the catalyst is formed by impregnatingwith the Group VIII metal and thereafter fluoriding the composite to thedesired degree by contacting the composite with gaseous HF and hydrogen.

References Cited UNITED STATES PATENTS 2,757,128 7/1956 Hemminger 2606672,728,713 12/1955 Kearby 260-667 2,884,469 4/1959 McCauley 2606673,054,833 9/1962 Donaldson et al 260667 DELBERT E. GANTZ, PrimaryExaminer.

V. OKEEFE, Assistant Examiner.

US. Cl. X.R. 252-441, 442

